Additives for electrochemical cells

ABSTRACT

Articles and methods including additives in electrochemical cells, are generally provided. As described herein, such electrochemical cells may comprise an anode, a cathode, an electrolyte, and optionally a separator. In some embodiments, at least one of the anode, the cathode, the electrolyte, and/or the optional separator may comprise an additive and/or additive precursor. For instance, in some cases, the electrochemical cell comprises an electrolyte and an additive and/or additive precursor that is soluble with and/or is present in the electrolyte. In some embodiments, the additive precursor comprises a disulfide bond. In certain embodiments, the additive is a carbon disulfide salt. In some cases, the electrolyte may comprise a nitrate.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/742,340, filed Jan. 14, 2020, which is a continuation of U.S.application Ser. No. 16/299,247 (now U.S. Pat. No. 10,541,448), filedMar. 12, 2019, which is a continuation of U.S. application Ser. No.15/349,140 (now U.S. Pat. No. 10,320,031), filed Nov. 11, 2016, whichclaims priority to U.S. Provisional Application No. 62/254,818, filedNov. 13, 2015, each of which is incorporated herein by reference in itsentirety.

FIELD

Articles and methods involving electrochemical cells including additivesare generally provided.

BACKGROUND

There has been considerable interest in recent years in developing highenergy density batteries with lithium-containing anodes. In such cells,cathode active material reduction and oxidation electrochemicalprocesses generally involve lithium ions. In particular, cathode activematerials may electrochemically intercalate lithium ions and/or producesoluble and insoluble lithium compounds during the charge-dischargeprocess. Rechargeable batteries with such metallic lithium electrodesgenerally exhibit limited cycle lifetimes. Accordingly, articles andmethods for increasing the cycle lifetime and/or other improvementswould be beneficial.

SUMMARY

Articles and methods including additives in electrochemical cells, aregenerally provided. The subject matter disclosed herein involves, insome cases, interrelated products, alternative solutions to a particularproblem, and/or a plurality of different uses of one or more systemsand/or articles.

In one aspect, electrochemical cells are provided. In some embodiments,an electrochemical cell comprises a first electrode, a second electrode,an electrolyte positioned between the first electrode and the secondelectrode, an additive having a structure as in Formula (I) and/or anadditive precursor having a structure as in Formula (II):

wherein each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², CR² ₂, and SiR² ₂, n is 1-6, and each R¹and R² can be the same or different, optionally connected, and areindependently selected from the group consisting of hydrogen, oxygen,sulfur, halogen, nitrogen, phosphorus, substituted or unsubstituted,branched or unbranched aliphatic, substituted or unsubstituted cyclic,substituted or unsubstituted, branched or unbranched acyclic,substituted or unsubstituted, branched or unbranched heteroaliphatic,substituted or unsubstituted, branched or unbranched acyl, substitutedor unsubstituted aryl, and substituted or unsubstituted heteroaryl.

In some embodiments, the electrochemical cell comprises a firstelectrode, a second electrode, an electrolyte positioned between thefirst electrode and the second electrode, an additive having a structureas in Formula (I) and/or an additive precursor having a structure as inFormula (II):

wherein each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², NR², CR² ₂, and SiR² ₂, n is 1-6, each R¹and R² can be the same or different, optionally connected, and areindependently selected from the group consisting of hydrogen, oxygen,sulfur, halogen, nitrogen, phosphorus, substituted or unsubstituted,branched or unbranched aliphatic, substituted or unsubstituted cyclic,substituted or unsubstituted, branched or unbranched acyclic,substituted or unsubstituted, branched or unbranched heteroaliphatic,substituted or unsubstituted, branched or unbranched acyl, substitutedor unsubstituted aryl, and substituted or unsubstituted heteroaryl, andthe additive and any additive precursor is present in theelectrochemical cell in a total amount of less than or equal to about 20wt % versus the total weight of the electrolyte and additive and/oradditive precursor, or the additive and any additive precursor ispresent in the electrochemical cell in a total amount of less than orequal to about 4 wt % versus the weight of each of the first and secondelectrodes.

In some embodiments, an electrochemical cell comprises a first electrodecomprising a first active electrode species, a second electrodecomprising a second active electrode species, an electrolyte positionedbetween the first electrode and the second electrode, an additive havinga structure as in Formula (I) and/or an additive precursor having astructure as in Formula (II):

wherein each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², NR², CR² ₂, and SiR² ₂, n is 1-6, each R¹and R² can be the same or different, optionally connected, and areindependently selected from the group consisting of hydrogen, oxygen,sulfur, halogen, nitrogen, phosphorus, substituted or unsubstituted,branched or unbranched aliphatic, substituted or unsubstituted cyclic,substituted or unsubstituted, branched or unbranched acyclic,substituted or unsubstituted, branched or unbranched heteroaliphatic,substituted or unsubstituted, branched or unbranched acyl, substitutedor unsubstituted aryl, and substituted or unsubstituted heteroaryl, andwherein the additive and any additive precursor is/are different fromthe first and second active electrode species.

In some embodiments, an electrochemical cell comprises a first electrodecomprising a first active electrode species, a second electrodecomprising a second active electrode species, an electrolyte positionedbetween the first electrode and the second electrode, lithiumbis-oxalatoborate, and an additive having a structure as in Formula (I):

wherein each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², NR², CR² ₂, and SiR² ₂, each R¹ and R² canbe the same or different, optionally connected, and are independentlyselected from the group consisting of hydrogen, oxygen, sulfur, halogen,nitrogen, phosphorus, substituted or unsubstituted, branched orunbranched aliphatic, substituted or unsubstituted cyclic, substitutedor unsubstituted, branched or unbranched acyclic, substituted orunsubstituted, branched or unbranched heteroaliphatic, substituted orunsubstituted, branched or unbranched acyl, substituted or unsubstitutedaryl, and substituted or unsubstituted heteroaryl, and wherein theadditive and any additive precursor is/are different from the first andsecond active electrode species.

In some embodiments, an electrochemical cell comprises a first electrodecomprising a first active electrode species, a second electrodecomprising a second active electrode species, an electrolyte positionedbetween the first electrode and the second electrode, lithiumbis-oxalatoborate and one or more of an ethyl xanthate salt, adiethiocarbamate salt, and an isopropyl xanthate salt.

In some embodiments, an electrochemical cell comprises a first electrodecomprising a first active electrode species, a second electrodecomprising a second active electrode species, an electrolyte positionedbetween the first electrode and the second electrode, lithiumbis-oxalatoborate, and an additive having a structure as in Formula (I):

wherein each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², NR², CR² ₂, and SiR² ₂, each R¹ and R² canbe the same or different, optionally connected, and are independentlyselected from the group consisting of hydrogen, oxygen, sulfur, halogen,nitrogen, phosphorus, substituted or unsubstituted, branched orunbranched aliphatic, substituted or unsubstituted cyclic, substitutedor unsubstituted, branched or unbranched acyclic, substituted orunsubstituted, branched or unbranched heteroaliphatic, substituted orunsubstituted, branched or unbranched acyl, substituted or unsubstitutedaryl, and substituted or unsubstituted heteroaryl, and wherein theadditive and any additive precursor is/are different from the first andsecond active electrode species. The second electrode is anintercalation electrode (e.g., a lithium intercalation electrode),optionally comprising one or more of Li_(x)CoO₂, Li_(x)NiO₂, Li_(x)MnO₂,Li_(x)Mn₂O₄, Li_(x)FePO₄, Li_(x)CoPO₄, Li_(x)MnPO₄, and Li_(x)NiPO₄,where (0<x≤1), and LiNi_(x)Mn_(y)Co_(z)O₂ where (x+y+z=1).

In another aspect, methods are provided. In some embodiments, a methodcomprises introducing into an electrochemical cell an additive having astructure as in Formula (I) and/or an additive precursor having astructure as in Formula (II):

wherein each occurrence of Q is independently selected from the groupconsisting of Se, O, S, NR², PR², CR² ₂, and SiR² ₂, n is 1-6, each R¹and R² can be the same or different, optionally connected, and areindependently selected from the group consisting of hydrogen, oxygen,sulfur, halogen, nitrogen; phosphorus; substituted or unsubstituted,branched or unbranched aliphatic, substituted or unsubstituted cyclic,substituted or unsubstituted, branched or unbranched acyclic,substituted or unsubstituted, branched or unbranched heteroaliphatic,substituted or unsubstituted, branched or unbranched acyl, substitutedor unsubstituted aryl, and substituted or unsubstituted heteroaryl, andwherein the electrode comprises active electrode species that is/aredifferent from the additive and any additive precursor.

In some embodiments, a method comprises introducing into anelectrochemical cell or a component of an electrochemical cell anadditive having a structure as in Formula (I) and/or an additiveprecursor having a structure as in Formula (II):

wherein each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², CR² ₂, and SiR² ₂, n is 1-6, and each R¹and R² can be the same or different, optionally connected, and areindependently selected from the group consisting of hydrogen, oxygen,sulfur, halogen, nitrogen, phosphorus, substituted or unsubstituted,branched or unbranched aliphatic, substituted or unsubstituted cyclic,substituted or unsubstituted, branched or unbranched acyclic,substituted or unsubstituted, branched or unbranched heteroaliphatic,substituted or unsubstituted, branched or unbranched acyl, substitutedor unsubstituted aryl, and substituted or unsubstituted heteroaryl.

In certain embodiments involving the methods described above and herein,an introducing step comprises adding to an electrolyte the additivehaving a structure as in Formula (I) and/or the additive precursorhaving a structure as in Formula (II). In certain embodiments involvingthe methods described above and herein, an introducing step comprisesapplying a coating to at least a portion of a surface of an electrode,the coating comprises the additive having a structure as in Formula (I)and/or the additive precursor having a structure as in Formula (II).

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the electrochemical cell comprises afirst electrode comprising a first active electrode species and a secondelectrode comprising a second active electrode species, wherein thefirst and second active electrode species are different from theadditive and the additive precursor.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive and/or additiveprecursor is polyanionic and/or a salt.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive comprises a cationselected from the group consisting of Li⁺, Na⁺, K⁺, Cs⁺, Rb⁺, Ca⁺²,Mg⁺², substituted or unsubstituted ammonium, guanidinium andimidazolium.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive and/or additiveprecursor comprises a xanthate group.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, each R¹ is C₂H₅ and/or each R² isC₂H₅.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, Q is oxygen or sulfur.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, n=1.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, at least a portion of the additiveand/or additive precursor is in solid form.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, at least a portion of the additiveand/or additive precursor is dissolved in the electrolyte.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive and/or additiveprecursor is at least partially soluble in the electrolyte.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive and/or additiveprecursor is disposed on and/or within the first electrode and/or thesecond electrode.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive and/or additiveprecursor is present in the electrolyte.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive and any additiveprecursor is present in the electrolyte in a total amount rangingbetween about 0.5 wt % and about 20 wt % versus the total weight of theelectrolyte and additive and/or additive precursor.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive and any additiveprecursor is present in the electrolyte in a total amount rangingbetween about 0.5 wt % and about 10 wt % versus the weight of each ofthe first and second electrodes.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive and/or additiveprecursor is disposed on and/or within a separator positioned betweenthe first electrode and the second electrode.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the additive and/or additiveprecursor is present in a reservoir positioned between the firstelectrode and the second electrode.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the electrolyte comprises a nitrateselected from the group consisting of LiNO₃, guanidine nitrate, andpyridine nitrate.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the electrolyte comprises one ormore of a carbonate, a hexafluorophosphate, 1,3-dioxolane,1,2-dimethoxyethane, a sulfonimide, sulfones, sulfolanes, esters ofcarbonic acid, and/or a nitrate containing compound.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the first active electrode speciescomprises lithium and/or the second active electrode species comprisessulfur.

In certain embodiments involving the electrochemical cells and/ormethods described above and herein, the second electrode is anintercalated electrode.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIGS. 1A-1F are a schematics of articles incorporating additives and/oradditive precursors, according to some embodiments; and

FIGS. 2-5 show plots of cycling behavior of electrochemical cellsincorporating additives, according to some embodiments.

DETAILED DESCRIPTION

Articles and methods involving electrochemical cells including additivesare generally provided. In some embodiments, an electrochemical cell mayinclude a first electrode, a second electrode, an electrolyte, andoptionally a separator. In some embodiments, at least one of the firstelectrode, second electrode, electrolyte, and/or optional separator mayinclude an additive and/or additive precursor incorporated therein. Forinstance, in some cases the electrolyte includes an additive such as acarbon disulfide salt and/or an additive precursor that is solublewithin the electrolyte and can form the additive upon cycling of theelectrochemical cell.

Advantageously, an electrochemical cell comprising one or more additivesand/or additive precursors described herein may offer one or moreadvantages over electrochemical cells that do not include such anadditive or additive precursor, including, but not limited to,increasing cycle lifetimes, providing improved lithium morphologies,increasing the compaction of lithium, and/or reducing the depletion oflithium during charge/discharge of an electrochemical cell.

The disclosed additives and additive precursors may be incorporated intovarious electrochemical cells. In some cases, the electrochemical cellmay be a lithium-based electrochemical cell, such as a lithium-sulfurelectrochemical cell, a lithium-ion electrochemical cell, a lithiummetal-lithium-ion electrochemical cell, an intercalated lithium metaloxide electrochemical cell, an intercalated lithium metal phosphateelectrochemical cell.

The additives and/or additive precursors may be included in any suitableform in an electrochemical cell, as described in more detail below. Insome embodiments, the additives and/or additive precursors may be added,in some cases, as a solid (e.g., a salt, as particles) incorporatedwithin the cathode, the anode, and/or the optional separator, or inparticular embodiments, as a solid layer on the cathode, the anode,and/or the optional separator. In some such embodiments, the solidadditive and/or additive precursor may be soluble or partially solublein the electrolyte. In some cases, upon cycling of the electrochemicalcell, the additive or additive precursor may remain in the component towhich the additive or additive precursor was originally included (e.g.,upon fabrication of electrochemical cell). In other cases, at least aportion of the additive or additive precursor may leach out of thecomponent to which the additive or additive precursor was originallyincluded, and migrate into the electrolyte. In other embodiments, theadditive or additive precursor may be included in the electrolyte (e.g.,in soluble or partially-soluble form) upon fabrication of theelectrochemical cell. Combinations of such configurations is alsopossible.

In some embodiments, the additive comprises a structure as in Formula(I):

wherein Q is selected from the group consisting of Se, O, S, PR², NR²,CR² ₂, and SiR² ₂, and each R¹ and R² can be the same or different,optionally connected, and are independently selected from the groupconsisting of hydrogen; oxygen; sulfur; halogen; halide; nitrogen;phosphorus; substituted or unsubstituted, branched or unbranchedaliphatic; substituted or unsubstituted cyclic; substituted orunsubstituted, branched or unbranched acyclic; substituted orunsubstituted, branched or unbranched heteroaliphatic; substituted orunsubstituted, branched or unbranched acyl; substituted or unsubstitutedaryl; and substituted or unsubstituted heteroaryl.

In certain embodiments, Q is independently selected from the groupconsisting of Se, O, S, PR², CR² ₂, and SiR² ₂, and each R¹ and R² canbe the same or different, optionally connected, and are independentlyselected from the group consisting of hydrogen; oxygen; sulfur; halogen;halide; nitrogen; phosphorus; substituted or unsubstituted, branched orunbranched aliphatic; substituted or unsubstituted cyclic; substitutedor unsubstituted, branched or unbranched acyclic; substituted orunsubstituted, branched or unbranched heteroaliphatic; substituted orunsubstituted, branched or unbranched acyl; substituted or unsubstitutedaryl; and substituted or unsubstituted heteroaryl.

In certain embodiments, Q is independently selected from the groupconsisting of Se, O, S, NR², PR², CR² ₂, and SiR² ₂. In a particularembodiment, Q is sulfur. In another embodiment, Q is NR². In someembodiments, the additive is a xanthate salt comprising a structure asin Formula (I) such that Q is oxygen. In certain embodiments, theadditive is a dithiocarbamate salt comprising a structure in Formula (I)such that Q is nitrogen.

In an exemplary embodiment, the additive comprises a structure as inFormula (I) wherein Q is oxygen and R¹ is C₂H₅. In another exemplaryembodiment, the additive comprises a structure as in Formula (I) whereinQ is sulfur and R¹ is C₂H₅. In yet another exemplary embodiment, theadditive comprises a structure as in Formula (I) wherein Q is NR², andR¹ and R² are each C₂H₅.

In certain embodiments, the additive comprising a structure as inFormula (I) further comprises a cation. In certain embodiments, thecation is selected from the group consisting of Li⁺, Na⁺, K⁺, Cs⁺, Rb⁺,Ca⁺², Mg⁺², substituted or unsubstituted ammonium, and organic cationssuch as guanidinium or imidazolium. In some cases, the additive may bepolyanionic.

In an exemplary embodiment, the additive is potassium ethyl xanthatehaving a structure as in:

In another exemplary embodiment, the additive is lithium diethyldithiocarbamate having a structure as in:

In yet another exemplary embodiment, the additive is potassium isopropylxanthate having a structure as in:

Those skilled in the art would understand that additional structures andcations are also possible based upon the teachings of thisspecification.

As described herein, in some embodiments, the additive is derived froman additive precursor. In certain embodiments, the electrochemical cellcomprises the additive precursor such that, for example, the additiveprecursor oxidizes into an additive as described herein after beingincorporated into the electrochemical cell. For instance, in someembodiments, the additive may form from the additive precursor duringcharge/discharge of the electrochemical cell. For example, in somecases, the additive precursor may be added to the electrochemical cell(e.g., in the electrolyte, as part of a first or second electrode, aspart of a layer in the cell) where at least a portion of the additiveprecursor forms an additive as described herein.

In some embodiments, the additive precursor comprises a structure as inFormula (II):

wherein each Q is independently selected from the group consisting ofSe, O, S, PR², NR², CR² ₂, and SiR² ₂, and each R¹ and R² can be thesame or different, optionally connected, and are independently selectedfrom the group consisting of hydrogen; oxygen; sulfur; halogen; halide;nitrogen; phosphorus; substituted or unsubstituted, branched orunbranched aliphatic; substituted or unsubstituted cyclic; substitutedor unsubstituted, branched or unbranched acyclic; substituted orunsubstituted, branched or unbranched heteroaliphatic; substituted orunsubstituted, branched or unbranched acyl; substituted or unsubstitutedaryl; and substituted or unsubstituted heteroaryl. In certainembodiments, each occurrence of Q is independently selected from thegroup consisting of Se, O, S, NR², PR², CR² ₂, and SiR² ₂.

In some cases, each Q may be the same or different and selected from thegroup consisting of oxygen, sulfur, and NR². In a particular embodiment,each Q is the same and is sulfur. In another embodiment, each Q is thesame and is NR². In some embodiments, each Q is the same and is oxygen.

In an exemplary embodiment the additive precursor comprises a structureas in Formula (II) wherein each Q is the same and oxygen and R¹ is C₂H₅.In another exemplary embodiment, the additive precursor comprises astructure as in Formula (II) wherein each Q is the same and is sulfurand R¹ is C₂H₅. In yet another exemplary embodiment, the additiveprecursor comprises a structure as in Formula (II) wherein each Q is thesame and is NR², wherein R¹ and R² are each C₂H₅.

In some embodiments, n is 1 (such that the additive precursor comprisesa disulfide bridge). In certain embodiments, n is 2-6 (such that theadditive precursor comprises a polysulfide). In some cases, n is 1, 2,3, 4, 5, 6, or combination thereof (e.g., 1-3, 2-4, 3-5, 4-6, 1-4, or1-6).

In certain embodiments, the additive and any additive precursor is/aredifferent from the first and second active electrode species (e.g., inembodiments in which two electrodes including different active electrodespecies are present). For example, in some embodiments, the additivehaving a structure as in Formula (I) and/or the additive precursorhaving a structure as in Formula (II) is added to an electrochemicalcell having a first electrode (e.g., including a first active electrodespecies comprising lithium metal) and a second electrode (e.g.,including a second active electrode species comprising sulfur). In otherembodiments, other electroactive species that are not the same speciesas (or derivatives of) the additive and/or additive precursor can beused. Active electrode species (e.g., anode active electrode species,cathode active electrode species) are described in more detail, below.The addition of additives and additive precursors is also described inmore detail, below.

The additive and additive precursor may be present in an electrochemicalcell in any suitable amount. The additive and additive precursor may bepresent, in some cases, in the electrochemical cell in an amount lessthan or equal to about 20 wt % versus the total weight of theelectrolyte and additive and/or additive precursor. For example, in someembodiments, the total weight of the additive and additive precursorpresent in the electrochemical cell is less than or equal to about 20 wt%, less than or equal to about 18 wt %, less than or equal to about 15wt %, less than or equal to about 12 wt %, less than or equal to about10 wt %, less than or equal to about 8 wt %, less than or equal to about6 wt %, less than or equal to about 5 wt %, less than or equal to about4 wt %, less than or equal to about 3 wt %, less than or equal to about2 wt %, or less than or equal to about 1 wt % versus the total weight ofthe electrolyte and additive and/or additive precursor. In certainembodiments, the total weight of the additive and additive precursorpresent in the electrochemical cell is greater than about 0.5 wt %,greater than about 1 wt %, greater than about 2 wt %, less than or equalto about 3 wt %, greater than about 4 wt %, greater than about 6 wt %,greater than about 8 wt %, greater than about 10 wt %, or greater thanabout 15 wt % versus the total weight of the electrolyte and additiveand/or additive precursor. Combinations of the above-referenced rangesare also possible (e.g., between about 0.5 wt % and about 20 wt %,between about 1 wt % and about 8 wt %, between about 4 wt % and about 10wt %, between about 6 wt % and about 15 wt %, between about 8 wt % andabout 20 wt %). Other ranges are also possible. In some embodiments, thewt % of additive and additive precursor is measured prior to first useor first discharge of the electrochemical cell. Methods for determiningthe weight percentage of the additive and additive precursor within theelectrolyte are known within the art and may include, in someembodiments, weighing the additive and additive precursor and theelectrolyte before adding the additive and/or additive precursor to theelectrolyte. In other embodiments, the wt % is measured at a point intime during the cycle life of the cell. In some such embodiments, thecycling of an electrochemical cell may be stopped and the wt % of theelectrolyte may be determined using, for example, gaschromatography-mass spectrometry. Other methods such as NMR, inductivelycoupled plasma mass spectrometry (ICP-MS), and elemental analysis canalso be used.

The amount of additive and additive precursor may be measured againstthe weight of one or more of the first or second electrodes. In someembodiments, the additive and additive precursor may be present in theelectrochemical cell in an amount less than or equal to about 10 wt %versus the weight of each of the first and second electrodes. Forexample, in some embodiments, the total weight of the additive andadditive precursor present in the electrochemical cell is less than orequal to about 10 wt %, less than or equal to about 8 wt %, less than orequal to about 6 wt %, less than or equal to about 4 wt %, less than orequal to about 2 wt %, or less than or equal to about 1 wt % versus theweight of each of the first and second electrodes. In certainembodiments, the total weight of the additive and additive precursorpresent in the electrochemical cell is greater than about 0.5 wt %,greater than about 1 wt %, greater than about 2 wt %, greater than about4 wt %, greater than about 6 wt %, or greater than about 8 wt % versusthe weight of each of the first and second electrodes. Combinations ofthe above-referenced ranges are also possible (e.g., between about 0.5wt % and about 10 wt %, between about 1 wt % and about 4 wt %, betweenabout 2 wt % and about 6 wt %, between about 4 wt % and about 8 wt %,between about 6 wt % and about 10 wt %). Other ranges are also possible.In some embodiments, the wt % of additive and additive precursor ismeasured prior to first use or first discharge of the electrochemicalcell. Methods for determining the weight percentage of the additive andadditive precursor within a layer (e.g., an electrode, a separator) ofthe electrochemical cell are known within the art and may include, insome embodiments, weighing the additive and additive precursor and thelayer before adding the additive and/or additive precursor to the layer.In other embodiments, the wt % is measured at any point in time duringthe cycle life of the cell. In some such embodiments, the cycling of anelectrochemical cell may be stopped and the wt % of the electrolyte maybe determined using, for example, gas chromatography-mass spectrometry.Other methods such as NMR, inductively coupled plasma mass spectrometry(ICP-MS), and elemental analysis can also be used.

While many embodiments described herein relate to lithium-sulfur and/orlithium-ion electrochemical cells, it is to be understood that theadditives and/or additive precursors described herein may be used in anysuitable electrochemical cell, such as analogous alkali metal/sulfurelectrochemical cells (including alkali metal anodes). As noted aboveand as described in more detail herein, in some embodiments, theadditive and/or additive precursor layer is incorporated into anelectrochemical cell as a layer adjacent an electrode. In some cases,the electrochemical cell may be fabricated by providing an electrode, anadditive layer comprising the additive and/or additive precursor, and anelectrolyte layer.

Turning now to the figures, FIG. 1A shows an example of an article thatcan be incorporated into an electrochemical cell. Article 10 includes anelectrode 20 (e.g., an anode or a cathode) that comprises anelectroactive material (e.g., lithium metal) and an electrolyte 40adjacent the electrode. The electrode may include an electroactivematerial (e.g., an anode active electrode material, a cathode activeelectrode material). The electrolyte can function as a medium for thestorage and transport of ions. The electrolyte may have any suitableconfiguration such as a liquid electrolyte, a solid electrolyte, or agel polymer electrolyte, as described in more detail herein. In someembodiments, the additive and/or additive precursor may be at leastpartially soluble in an electrolyte.

In some embodiments, the additive (e.g., comprising a structure as inFormula (I)) and/or the additive precursor (e.g., comprising a structureas in Formula (II)) may be added to the electrolyte prior or during toformation of the electrochemical cell such that at least a portion (orall) of the additive and/or additive precursor dissolves within theelectrolyte. In certain embodiments, the additive and/or additiveprecursor is added to the electrolyte after formation of theelectrochemical cell (e.g., during cycling). For example, the additiveand/or additive precursor may initially be a part of a differentcomponent of the electrochemical cell (e.g., as part of the anode,cathode, and/or separator), such as upon formation of theelectrochemical cell. In some cases, minimal or no amount of theadditive and/or additive precursor may be present in the electrolyte atthis time. After a certain amount of time and/or upon use (e.g., firstuse or first discharge, subsequent use) of the electrochemical cell, allor portions of the additive and/or additive precursor may migrate intothe electrolyte.

In certain embodiments, at least a portion of (or all of) the additiveand/or additive precursor may be in solid form (e.g., as one or moreparticles or as one or more solid structures) in the electrochemicalcell at at least one point in time in the life of the electrochemicalcell (e.g., prior to first use or first discharge of the electrochemicalcell). In some such embodiments, the solid additive and/or additiveprecursor may advantageously act as a reservoir of additive such thatthe additive and/or additive precursor dissolves over time in theelectrolyte (e.g., during charge/discharge of the electrochemical cell).For example, as shown illustratively in FIG. 1B, an article 11 includeselectrode 20 including an electroactive material, electrolyte 40adjacent electrode 20, and a reservoir 30 comprising the additive and/oradditive precursor. In some cases, the solid additive and/or additiveprecursor is in the form of a solid particle. For example, in someembodiments, the electrochemical cell comprises a plurality of additivesolid particles and/or a plurality of additive precursor solid particles(e.g., in the electrolyte, in an electrode, in a layer, and/or in aseparator).

If particles of additives and/or additive precursors are present, theparticles may have any suitable size. In some embodiments, an averagelargest cross-sectional dimension of a plurality of additive and/oradditive precursor solid particles may be, for example, less than orequal to 100 microns, less than or equal to about 50 microns, less thanor equal to about 25 microns, less than or equal to about 10 microns,less than or equal to about 5 microns, less or equal to about 2 microns,less than or equal to about 1 micron, less than or equal to about 800nm, less than or equal to about 500 nm, or less than or equal to about200 nm. In some embodiments, the average largest cross-sectionaldimension of the plurality of particles may be greater than or equal toabout 100 nm, greater than or equal to about 200 nm, greater than orequal to about 500 nm, greater than or equal to about 800 nm, greaterthan or equal to about 1 micron, greater than or equal to about 2microns, greater than or equal to about 5 microns, greater than or equalto about 10 microns, greater than or equal to about 25 microns, orgreater than or equal to about 50 microns. Combinations of theabove-referenced ranges are also possible (e.g., a largestcross-sectional dimension of less than about 100 microns and greaterthan about 100 nm).

The average largest cross-sectional dimension of the plurality ofparticles may be determined, for example, by imaging the particles witha scanning electron microscope (SEM). An image may be acquired at amagnification between about 10× to about 100,000×, depending on theoverall dimensions of the plurality of particles. Those skilled in theart would be capable of selecting an appropriate magnification forimaging the sample. The average largest cross-sectional dimension of theplurality of particles can be determined by taking the longestcross-sectional dimension of each particle in the image and averagingthe longest cross-sectional dimensions (e.g., averaging the longestcross-sectional dimensions for 50 particles).

In some embodiments, the additive and/or additive precursor is in solidform and deposited as a layer on or adjacent one or more layers in theelectrochemical cell. Referring to FIG. 1C, in some embodiments, anarticle 12 comprises electrode 20, electrolyte 40 adjacent electrode 20,and an additive layer 32 disposed on or adjacent at least a portion ofelectrode active surface 20′. As shown illustratively in the figure, theadditive layer may be in direct contact with the electrolyte, or one ormore intervening layer(s) may be present (not shown). In someembodiments, the additive layer may be adjacent an anode. In someembodiments, the additive layer may be adjacent a cathode. The additivelayer can include, for example, the additive and/or the additiveprecursor and any suitable optional components (e.g., a filler, apolymer, a metal, a ceramic, porous silica sol-gel). In someembodiments, a component included in an additive layer comprises apolymeric binder. Non-limiting examples of suitable polymeric bindersinclude polyethylene oxide, polyethylene, and polyvinylidene fluoride.In certain embodiments, the component (e.g., a component comprising apolymeric binder) may be soluble with and/or may substantially dissolvein an electrolyte. In some cases, the optional component may swell inthe presence of an electrolyte.

In certain embodiments, the electrochemical cell comprises a separatorand the additive layer may be deposited on at least a portion of asurface of the separator, or within the separator. For example, as shownillustratively in FIG. 1D, an article 13 comprises electrode 20,electrolyte 40 adjacent the electrode, and a separator 50 adjacent theelectrolyte. In some embodiments, the article comprises an additivelayer 32 disposed on at least a portion of separator 50 at separatorsurface 50′. The additive layer may advantageously serve as a reservoirsuch that the additive and/or additive precursor dissolves over time inthe electrolyte (e.g., during charge/discharge of the electrochemicalcell).

In some cases, the electrochemical cell comprises a first electrode(e.g., an anode), a second electrode (e.g., a cathode), and anelectrolyte disposed between the first and second electrodes. Forexample, as shown illustratively in FIG. 1E, article 14 comprises firstelectrode 20, second electrode 22, and electrolyte 40 disposed betweenthe first and second electrodes. In some embodiments, the additiveand/or additive precursor may be present as a solid additive layer onthe first electrode and/or the second electrode, as described herein. Insome embodiments, the additive and/or additive precursor may beincorporated into the electrode and/or the separator. For example, theadditive and/or additive precursor may be added (e.g., in solid form) toa slurry comprising an electroactive material prior to the formation ofan electrode. In some such embodiments, the electrode incorporating theadditive and/or additive precursor may serve as a reservoir such thatthe additive and/or additive precursor dissolves in an electrolyte incontact with the electrode and/or upon use of the electrochemical cell.

A layer referred to as being “disposed on,” “disposed between,” “on,” or“adjacent” another layer(s) means that it can be directly disposed on,disposed between, on, or adjacent the layer(s), or an intervening layermay also be present. For example, an additive layer described hereinthat is adjacent an anode or cathode may be directly adjacent (e.g., maybe in direct physical contact with) the anode or cathode, or anintervening layer (e.g., another protective layer) may be positionedbetween the anode and the additive layer. A layer that is “directlyadjacent,” “directly on,” or “in contact with,” another layer means thatno intervening layer is present. It should also be understood that whena layer is referred to as being “disposed on,” “disposed between,” “on,”or “adjacent” another layer(s), it may be covered by, on or adjacent theentire layer(s) or a part of the layer(s).

It should be appreciated that FIGS. 1A-1F are exemplary illustrationsand that not all components shown in the figure need be present, or,additional components not shown in the figure may be present. Forexample, an additive layer 32 may be disposed directly on one or moreelectrodes, or may be disposed on a protective layer in contact with theelectrode in some embodiments. In an exemplary embodiment, as shown inFIG. 1F, additive layer 32 may be disposed directly on protective layer60 which is in direct contact with electrode 20. Other configurationsare also possible. Protective layers are described in more detail below.

In some cases, the additive precursor may be added (e.g., as a solid, asa film, dissolved in solution) to an electrolyte, an electrode, aseparator, and/or any additional layers of an electrochemical cell in anamount described above, e.g., prior to formation, prior to first use orfirst discharge, or during use, of the electrochemical cell. In somesuch embodiments, the additive precursor (e.g., having a structure as inFormula (II)) may react and/or solubilize with the electrolyte such thatat least a portion of the additive precursor present in theelectrochemical cell forms the additive (e.g., having a structure as inFormula (I)). In some cases, a mixture comprising the additive and theadditive precursor may be provided to the electrochemical cell, or acomponent of an electrochemical cell, as described herein. The ratio ofthe additive and the additive precursor may be, for example, at leastabout 1:1000, at least about 1:500, at least about 1:200, at least about1:100, at least about 1:50, at least about 1:20, at least about 1:10, atleast about 1:5, at least about 1:2, at least about 1:1, at least about2:1, at least about 5:1, at least about 10:1, at least about 20:1, atleast about 50:1, at least about 100:1, at least about 200:1, or atleast about 500:1. In certain embodiments, the ratio of the additive andthe additive precursor may be less than or equal to about 1000:1, lessthan or equal to about 500:1, less than or equal to about 200:1, lessthan or equal to about 100:1, less than or equal to about 50:1, lessthan or equal to about 20:1, less than or equal to about 10:1, less thanor equal to about 5:1, less than or equal to about 2:1, less than orequal to about 1:1, less than or equal to about 1:2, less than or equalto about 1:5, less than or equal to about 1:10, less than or equal toabout 1:20, less than or equal to about 1:50, less than or equal toabout 1:100, less than or equal to about 1:200, or less than or equal toabout 1:500. Combinations of the above-referenced ranges are alsopossible (e.g., at least about 1:1000 and less than or equal to about1000:1). Other ranges are also possible. In certain embodiments, amixture comprising the additive with substantially no additive precursormay be provided to the electrochemical cell or component of a cell. Insome embodiments, a mixture comprising the additive precursor withsubstantially no additive may be provided to the electrochemical cell orcomponent of a cell. Methods for determining the ratio of the additiveand additive are known within the art and may include, in someembodiments, weighing the additive and additive precursor before mixingthe additive and/or additive precursor. In other embodiments, the ratiois measured at a point in time during the cycle life of the cell. Insome such embodiments, the cycling of an electrochemical cell may bestopped and the ratio is determined by measuring the wt % of theadditive and the wt % of the additive precursor using gaschromatography-mass spectrometry. Other methods are also possible asdescribed herein.

The additive and/or additive precursor may be deposited on one or morelayers of an electrochemical cell (e.g., an anode, a cathode, aseparator, a protective layer) using any suitable method. Non-limitingexamples of suitable methods for depositing the additive and/or additiveprecursor on a layer of the electrochemical cell include vacuumsputtering, thermal evaporation, solution coating, wet spraying, dryspraying, aerosol deposition, vacuum deposition, particle electrostaticdeposition, solvent evaporation, and the like. In an exemplaryembodiment, the additive and/or additive precursor may be mixed with asolvent (and/or other materials such as a filler, a polymer, a metal, aceramic) and coated on a layer of the electrochemical cell (such as anelectrode). The coating may be dried, in some such embodiments, suchthat the additive and/or additive precursor is in solid form therebyforming an additive layer.

The additive layer, if present, may have any suitable thickness. In someembodiments, the additive layer (e.g., comprising the additive and/oradditive precursor) described herein may have a thickness of at leastabout 10 nm at least about 20 nm, at least about 50 nm, at least about100 nm, at least about 200 nm, at least about 500 nm, at least about 1micron, at least about 5 microns, at least about 10 microns, at leastabout 15 microns, at least about 20 microns, at least about 25 microns,at least about 30 microns, at least about 40 microns, at least about 50microns, at least about 70 microns, at least about 100 microns, at leastabout 200 microns, at least about 500 microns, or at least about 1 mm.In some embodiments, the thickness of the additive layer is less than orequal to about 1 mm, less than or equal to about 500 microns, less thanor equal to about 200 microns, less than or equal to about 100 microns,less than or equal to about 70 microns, less than or equal to about 50microns, less than or equal to about 40 microns, less than or equal toabout 30 microns, less than or equal to about 20 microns, less than orequal to about 10 microns, less than or equal to about 5 microns, lessthan or equal to about 1 micron, less than or equal to about 500 nm,less than or equal to about 200 nm, less than or equal to about 100 nm,less than or equal to about 50 nm, or less than or equal to about 20 nm.Other values are also possible. Combinations of the above-noted rangesare also possible.

The average thickness of the additive layer can be determined by, forexample, using a drop gauge or scanning electron microscopy (SEM).Briefly, the additive layer can be imaged along a cross-section (e.g.,by cutting the additive layer) after formation and the image may beacquired by SEM. The average thickness may be determined by taking anaverage of the thickness of the sample at several different locationsalong the cross-section (e.g., at least 5 locations). Those skilled inthe art would be capable of selecting an appropriate magnification forimaging the sample.

As described herein, an electrochemical cell or an article for use in anelectrochemical cell may include an electrode comprising an activeelectrode species. In some embodiments, a first electrode describedherein comprises a first active electrode species. In some cases, thefirst layer may be an anode (e.g., an anode of an electrochemical cell).In some embodiments, an additive layer comprising the additive and/oradditive precursor is deposited on an anode. In certain embodiments, theadditive and/or additive precursor is incorporated into the electrode(e.g., by mixing with an active electrode material prior to theformation of the anode).

Suitable active electrode materials for use as anode active electrodespecies in the electrochemical cells described herein include, but arenot limited to, lithium metal such as lithium foil and lithium depositedonto a conductive substrate, and lithium alloys (e.g., lithium-aluminumalloys and lithium-tin alloys). Lithium can be contained as one film oras several films, optionally separated by a protective material such asa ceramic material or an ion conductive material described herein.Suitable ceramic materials include silica, alumina, or lithiumcontaining glassy materials such as lithium phosphates, lithiumaluminates, lithium silicates, lithium phosphorous oxynitrides, lithiumtantalum oxide, lithium aluminosulfides, lithium titanium oxides,lithium silcosulfides, lithium germanosulfides, lithium aluminosulfides,lithium borosulfides, and lithium phosphosulfides, and combinations oftwo or more of the preceding. Suitable lithium alloys for use in theembodiments described herein can include alloys of lithium and aluminum,magnesium, silicium (silicon), indium, and/or tin. While these materialsmay be preferred in some embodiments, other cell chemistries are alsocontemplated. In some embodiments, the anode may comprise one or morebinder materials (e.g., polymers, etc.).

In some embodiments, the thickness of the anode may vary from, e.g.,about 2 to 200 microns. For instance, the anode may have a thickness ofless than 200 microns, less than 100 microns, less than 50 microns, lessthan 25 microns, less than 10 microns, or less than 5 microns. Incertain embodiments, the anode may have a thickness of greater than orequal to about 2 microns, greater than or equal to about 5 microns,greater than or equal to about 10 microns, greater than or equal toabout 25 microns, greater than or equal to about 50 microns, greaterthan or equal to about 100 microns, or greater than or equal to about150 microns. Combinations of the above-referenced ranges are alsopossible (e.g., between about 2 microns and about 200 microns, betweenabout 2 microns and about 100 microns, between about 5 microns and about50 microns, between about 5 microns and about 25 microns, between about10 microns and about 25 microns). Other ranges are also possible. Thechoice of the thickness may depend on cell design parameters such as theexcess amount of lithium desired, cycle life, and the thickness of thecathode electrode.

In some embodiments, an electrode described herein may be a cathode(e.g., a cathode of an electrochemical cell). For instance, in someembodiments, an additive layer comprising the additive and/or additiveprecursor is deposited on a cathode. In certain embodiments, theadditive and/or additive precursor is incorporated into the cathode(e.g., by mixing with an cathode active electrode material prior to theformation of the cathode).

Suitable active electrode materials for use as cathode active electrodespecies in the cathode of the electrochemical cells described herein mayinclude, but are not limited to, electroactive transition metalchalcogenides, electroactive conductive polymers, sulfur, carbon, and/orcombinations thereof. As used herein, the term “chalcogenides” pertainsto compounds that contain one or more of the elements of oxygen, sulfur,and selenium. Examples of suitable transition metal chalcogenidesinclude, but are not limited to, the electroactive oxides, sulfides, andselenides of transition metals selected from the group consisting of Mn,V, Cr, Ti, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re,Os, and Ir. In one embodiment, the transition metal chalcogenide isselected from the group consisting of the electroactive oxides ofnickel, manganese, cobalt, and vanadium, and the electroactive sulfidesof iron. In certain embodiments, the cathode may include as anelectroactive species elemental sulfur, sulfides, and/or polysulfides.In other embodiments, an intercalation electrode (e.g., alithium-intercalation cathode) may be used. Non-limiting examples ofsuitable materials that may intercalate ions of an electroactivematerial (e.g., alkaline metal ions) include oxides, titanium sulfide,and iron sulfide. Additional examples include Li_(x)CoO₂, Li_(x)NiO₂,Li_(x)MnO₂, Li_(x)Mn₂O₄, Li_(x)FePO₄, Li_(x)CoPO₄, Li_(x)MnPO₄, andLi_(x)NiPO₄, where (0<x≤1), and LiNi_(x)Mn_(y)Co_(z)O₂ where (x+y+z=1).

In one embodiment, a cathode includes one or more of the followingmaterials: manganese dioxide, iodine, silver chromate, silver oxide andvanadium pentoxide, copper oxide, copper oxyphosphate, lead sulfide,copper sulfide, iron sulfide, lead bismuthate, bismuth trioxide, cobaltdioxide, copper chloride, manganese dioxide, and carbon. In anotherembodiment, the cathode active layer comprises an electroactiveconductive polymer. Examples of suitable electroactive conductivepolymers include, but are not limited to, electroactive andelectronically conductive polymers selected from the group consisting ofpolypyrroles, polyanilines, polyphenylenes, polythiophenes, andpolyacetylenes. Examples of conductive polymers include polypyrroles,polyanilines, and polyacetylenes.

In some embodiments, active electrode materials for use as cathodeactive materials in electrochemical cells described herein includeelectroactive sulfur-containing materials (e.g., lithium-sulfurelectrochemical cells). “Electroactive sulfur-containing materials,” asused herein, relates to cathode active materials which comprise theelement sulfur in any form, wherein the electrochemical activityinvolves the oxidation or reduction of sulfur atoms or moieties. Thenature of the electroactive sulfur-containing materials useful in thepractice of this invention may vary widely, as known in the art. Forexample, in one embodiment, the electroactive sulfur-containing materialcomprises elemental sulfur. In another embodiment, the electroactivesulfur-containing material comprises a mixture of elemental sulfur and asulfur-containing polymer. Thus, suitable electroactivesulfur-containing materials may include, but are not limited to,elemental sulfur and organic materials comprising sulfur atoms andcarbon atoms, which may or may not be polymeric. Suitable organicmaterials include those further comprising heteroatoms, conductivepolymer segments, composites, and conductive polymers.

In certain embodiments, the sulfur-containing material (e.g., in anoxidized form) comprises a polysulfide moiety, Sm, selected from thegroup consisting of covalent Sm moieties, ionic Sm moieties, and ionicSm₂-moieties, wherein m is an integer equal to or greater than 3. Insome embodiments, m of the polysulfide moiety Sm of thesulfur-containing polymer is an integer equal to or greater than 6 or aninteger equal to or greater than 8. In some cases, the sulfur-containingmaterial may be a sulfur-containing polymer. In some embodiments, thesulfur-containing polymer has a polymer backbone chain and thepolysulfide moiety Sm is covalently bonded by one or both of itsterminal sulfur atoms as a side group to the polymer backbone chain. Incertain embodiments, the sulfur-containing polymer has a polymerbackbone chain and the polysulfide moiety Sm is incorporated into thepolymer backbone chain by covalent bonding of the terminal sulfur atomsof the polysulfide moiety.

In some embodiments, the electroactive sulfur-containing materialcomprises more than 50% by weight of sulfur. In certain embodiments, theelectroactive sulfur-containing material comprises more than 75% byweight of sulfur (e.g., more than 90% by weight of sulfur).

As will be known by those skilled in the art, the nature of theelectroactive sulfur-containing materials described herein may varywidely. In some embodiments, the electroactive sulfur-containingmaterial comprises elemental sulfur. In certain embodiments, theelectroactive sulfur-containing material comprises a mixture ofelemental sulfur and a sulfur-containing polymer.

In certain embodiments, an electrochemical cell as described herein,comprises one or more cathodes comprising sulfur as a cathode activeelectrode species. In some such embodiments, the cathode includeselemental sulfur as a cathode active electrode species. In someembodiments, the additive is chosen such that the additive is differentfrom the anode active electrode species and different from the cathodeactive electrode species. In certain embodiments, the additive precursoris chosen such that the additive precursor is different from the anodeactive electrode species and different from the cathode active electrodespecies.

In some embodiments, the cathode comprises a nitrate or other N—Ocompound as described in more detail herein.

Referring again to FIG. 1F, an additive layer (e.g., additive layer 32)may be disposed directly on a protective layer (protective layer 60)which is in direct contact with an electrode (electrode 20), or disposedon a protective layer via an intervening layer. In some embodiments, theprotective layer is an ion-conductive layer.

In some embodiments, the protective layer or ion conductive layer is aceramic layer, a glassy layer, or a glassy-ceramic layer, e.g., an ionconducting ceramic/glass conductive to lithium ions. Suitable glassesand/or ceramics include, but are not limited to, those that may becharacterized as containing a “modifier” portion and a “network”portion, as known in the art. The modifier may include a metal oxide ofthe metal ion conductive in the glass or ceramic. The network portionmay include a metal chalcogenide such as, for example, a metal oxide orsulfide. For lithium metal and other lithium-containing electrodes, anion conductive layer may be lithiated or contain lithium to allowpassage of lithium ions across it. Ion conductive layers may includelayers comprising a material such as lithium nitrides, lithiumsilicates, lithium borates, lithium aluminates, lithium phosphates,lithium phosphorus oxynitrides, lithium silicosulfides, lithiumgermanosulfides, lithium oxides (e.g., Li₂O, LiO, LiO₂, LiRO₂, where Ris a rare earth metal), lithium lanthanum oxides, lithium titaniumoxides, lithium borosulfides, lithium aluminosulfides, and lithiumphosphosulfides, and combinations thereof. The selection of the ionconducting material will be dependent on a number of factors including,but not limited to, the properties of electrolyte, additive (and/oradditive precursor) and cathode used in the cell.

In one set of embodiments, the ion conductive layer is anon-electroactive metal layer. The non-electroactive metal layer maycomprise a metal alloy layer, e.g., a lithiated metal layer especiallyin the case where a lithium anode is employed. The lithium content ofthe metal alloy layer may vary from about 0.5% by weight to about 20% byweight, depending, for example, on the specific choice of metal, thedesired lithium ion conductivity, and the desired flexibility of themetal alloy layer. Suitable metals for use in the ion conductivematerial include, but are not limited to, Al, Zn, Mg, Ag, Pb, Cd, Bi,Ga, In, Ge, Sb, As, and Sn. Sometimes, a combination of metals, such asthe ones listed above, may be used in an ion conductive material.

The thickness of an ion conductive material layer may vary over a rangefrom about 1 nm to about 10 microns. For instance, the thickness of theion conductive material layer may be between 1-10 nm thick, between10-100 nm thick, between 100-1000 nm thick, between 1-5 microns thick,or between 5-10 microns thick. In some embodiments, the thickness of anion conductive material layer may be, for example, less than or equal to10 microns, less than or equal to 5 microns, less than or equal to 1000nm, less than or equal to 500 nm, less than or equal to 250 nm, lessthan or equal to 100 nm, less than or equal to 50 nm, less than or equalto 25 nm, or less than or equal to 10 nm. In certain embodiments, theion conductive layer may have a thickness of greater than or equal to 10nm, greater than or equal to 25 nm, greater than or equal to 50 nm,greater than or equal to 100 nm, greater than or equal to 250 nm,greater than or equal to 500 nm, greater than or equal to 1000 nm, orgreater than or equal to 1500 nm. Combinations of the above-referencedranges are also possible (e.g., a thickness of greater than or equal to10 nm and less than or equal to 500 nm). Other thicknesses are alsopossible. In some cases, the ion conductive layer has the same thicknessas a polymer layer.

The ion conductive layer may be deposited by any suitable method such assputtering, electron beam evaporation, vacuum thermal evaporation, laserablation, chemical vapor deposition (CVD), thermal evaporation, plasmaenhanced chemical vacuum deposition (PECVD), laser enhanced chemicalvapor deposition, and jet vapor deposition. The technique used maydepend on the type of material being deposited, the thickness of thelayer, etc.

In some embodiments, the ion conductive material is non-polymeric. Incertain embodiments, the ion conductive material is defined in part orin whole by a layer that is highly conductive toward lithium ions (orother ions) and minimally conductive toward electrons. In other words,the ion conductive material may be one selected to allow certain ions,such as lithium ions, to pass across the layer, but to impede electrons,from passing across the layer. In some embodiments, the ion conductivematerial forms a layer that allows only a single ionic species to passacross the layer (i.e., the layer may be a single-ion conductive layer).In other embodiments, the ion conductive material may be substantiallyconductive to electrons.

In some embodiments, the protective layer is a polymer layer comprisinga polymeric material. Suitable polymer layers for use in electrochemicalcells may be, for example, highly conductive towards lithium andminimally conductive towards electrons. Such polymers may include, forexample, ionically conductive polymers, sulfonated polymers, andhydrocarbon polymers. The selection of the polymer will be dependentupon a number of factors including the properties of electrolyte,additive, and cathode used in the cell. Suitable ionically conductivepolymers include, e.g., ionically conductive polymers known to be usefulin solid polymer electrolytes and gel polymer electrolytes for lithiumelectrochemical cells, such as, for example, polyethylene oxides.Suitable sulfonated polymers include, e.g., sulfonated siloxanepolymers, sulfonated polystyrene-ethylene-butylene polymers, andsulfonated polystyrene polymers. Suitable hydrocarbon polymers include,e.g., ethylene-propylene polymers, polystyrene polymers, and the like.

Polymer layers can also include crosslinked polymer materials formedfrom the polymerization of monomers such as alkyl acrylates, glycolacrylates, polyglycol acrylates, polyglycol vinyl ethers, polyglycoldivinyl ethers, and those described in U.S. Pat. No. 6,183,901 to Yinget al. of the common assignee for protective coating layers forseparator layers. For example, one such crosslinked polymer material ispolydivinyl poly(ethylene glycol). The crosslinked polymer materials mayfurther comprise salts, for example, lithium salts, to enhance ionicconductivity. In one embodiment, the polymer layer comprises acrosslinked polymer.

Other classes polymers that may be suitable for use in a polymer layerinclude, but are not limited to, polyamines (e.g., poly(ethylene imine)and polypropylene imine (PPI)); polyamides (e.g., polyamide (Nylon),poly(ϵ-caprolactam) (Nylon 6), poly(hexamethylene adipamide) (Nylon66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton)); vinyl polymers(e.g., polyacrylamide, poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyolefins(e.g., poly(butene-1), poly(n-pentene-2), polypropylene,polytetrafluoroethylene); polyesters (e.g., polycarbonate, polybutyleneterephthalate, polyhydroxybutyrate); polyethers (poly(ethylene oxide)(PEO), poly(propylene oxide) (PPO), poly(tetramethylene oxide) (PTMO));vinylidene polymers (e.g., polyisobutylene, poly(methyl styrene),poly(methylmethacrylate) (PMMA), poly(vinylidene chloride), andpoly(vinylidene fluoride)); polyaramides (e.g., poly(imino-1,3-phenyleneiminoisophthaloyl) and poly(imino-1,4-phenylene iminoterephthaloyl));polyheteroaromatic compounds (e.g., polybenzimidazole (PBI),polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT));polyheterocyclic compounds (e.g., polypyrrole); polyurethanes; phenolicpolymers (e.g., phenol-formaldehyde); polyalkynes (e.g., polyacetylene);polydienes (e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene);polysiloxanes (e.g., poly(dimethylsiloxane) (PDMS),poly(diethylsiloxane) (PDES), polydiphenylsiloxane (PDPS), andpolymethylphenylsiloxane (PMPS)); and inorganic polymers (e.g.,polyphosphazene, polyphosphonate, polysilanes, polysilazanes). Themechanical and electronic properties (e.g., conductivity, resistivity)of these polymers are known. Accordingly, those of ordinary skill in theart can choose suitable polymers for use in lithium batteries, e.g.,based on their mechanical and/or electronic properties (e.g., ionicand/or electronic conductivity), and/or can modify such polymers to beionically conducting (e.g., conductive towards single ions) and/orelectronically conducting based on knowledge in the art, in combinationwith the description herein. For example, the polymer materials listedabove may further comprise salts, for example, lithium salts (e.g.,LiSCN, LiBr, LiI, LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄,LiPF₆, LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity.

The polymeric materials can be selected or formulated to have suitablephysical/mechanical characteristics by, for example, tailoring theamounts of components of polymer blends, adjusting the degree ofcross-linking (if any), etc.

As described herein, in some embodiments, an electrochemical cellincludes a separator. The separator generally comprises a polymericmaterial (e.g., polymeric material that does or does not swell uponexposure to electrolyte). In some embodiments, the separator is locatedbetween the electrolyte and an electrode (e.g., an anode, a cathode).

In some embodiments, an additive layer comprising the additive and/oradditive precursor is deposited on a separator. In certain embodiments,the additive and/or additive precursor is incorporated into theseparator.

The separator can be configured to inhibit (e.g., prevent) physicalcontact between a first electrode and a second electrode, which couldresult in short circuiting of the electrochemical cell. The separatorcan be configured to be substantially electronically non-conductive,which can inhibit the degree to which the separator causes shortcircuiting of the electrochemical cell. In certain embodiments, all orportions of the separator can be formed of a material with a bulkelectronic resistivity of at least about 10⁴, at least about 10⁵, atleast about 10¹⁰, at least about 10¹⁵, or at least about 10²⁰Ohm-meters. Bulk electronic resistivity may be measured at roomtemperature (e.g., 25 degrees Celsius).

In some embodiments, the separator can be ionically conductive, while inother embodiments, the separator is substantially ionicallynon-conductive. In some embodiments, the average ionic conductivity ofthe separator is at least about 10⁻⁷ S/cm, at least about 10⁻⁶ S/cm, atleast about 10⁻⁵ S/cm, at least about 10⁻⁴ S/cm, at least about 10⁻²S/cm, at least about 10⁻¹ S/cm. In certain embodiments, the averageionic conductivity of the separator may be less than or equal to about 1S/cm, less than or equal to about 10⁻¹ S/cm, less than or equal to about10⁻² S/cm, less than or equal to about 10⁻³ S/cm, less than or equal toabout 10⁻⁴ S/cm, less than or equal to about 10⁻⁵ S/cm, less than orequal to about 10⁻⁶ S/cm, less than or equal to about 10⁻⁷ S/cm, or lessthan or equal to about 10⁻⁸ S/cm. Combinations of the above-referencedranges are also possible (e.g., an average ionic conductivity of atleast about 10⁻⁸ S/cm and less than or equal to about 10⁻¹ S/cm). Otherion conductivity is are also possible. Conductivity may be measured atroom temperature (e.g., 25 degrees Celsius).

In some embodiments, the average ion conductivity of the separator canbe determined by pressing the separator between two copper cylinders ata pressure of up to 3 tons/cm². In certain embodiments, the average ionconductivity (i.e., the inverse of the average resistivity) can bemeasured at 500 kg/cm² increments using a conductivity bridge (i.e., animpedance measuring circuit) operating at 1 kHz. In some suchembodiments, the pressure is increased until changes in average ionconductivity are no longer observed in the sample.

In some embodiments, the separator can be a solid. The separator may beporous to allow an electrolyte solvent to pass through it. In somecases, the separator does not substantially include a solvent (like in agel), except for solvent that may pass through or reside in the pores ofthe separator. In other embodiments, a separator may be in the form of agel.

A separator can be made of a variety of materials. The separator may bepolymeric in some instances, or formed of an inorganic material (e.g.,glass fiber filter papers) in other instances. Examples of suitableseparator materials include, but are not limited to, polyolefins (e.g.,polyethylenes, poly(butene-1), poly(n-pentene-2), polypropylene,polytetrafluoroethylene), polyamines (e.g., poly(ethylene imine) andpolypropylene imine (PPI)); polyamides (e.g., polyamide (Nylon),poly(ϵ-caprolactam) (Nylon 6), poly(hexamethylene adipamide) (Nylon66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton®) (NOMEX®) (KEVLAR®));polyether ether ketone (PEEK); vinyl polymers (e.g., polyacrylamide,poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyesters(e.g., polycarbonate, polybutylene terephthalate, polyhydroxybutyrate);polyethers (poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO),poly(tetramethylene oxide) (PTMO)); vinylidene polymers (e.g.,polyisobutylene, poly(methyl styrene), poly(methylmethacrylate) (PMMA),poly(vinylidene chloride), and poly(vinylidene fluoride)); polyaramides(e.g., poly(imino-1,3-phenylene iminoisophthaloyl) andpoly(imino-1,4-phenylene iminoterephthaloyl)); polyheteroaromaticcompounds (e.g., polybenzimidazole (PBI), polybenzobisoxazole (PBO) andpolybenzobisthiazole (PBT)); polyheterocyclic compounds (e.g.,polypyrrole); polyurethanes; phenolic polymers (e.g.,phenol-formaldehyde); polyalkynes (e.g., polyacetylene); polydienes(e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene); polysiloxanes(e.g., poly(dimethylsiloxane) (PDMS), poly(diethylsiloxane) (PDES),polydiphenylsiloxane (PDPS), and polymethylphenylsiloxane (PMPS)); andinorganic polymers (e.g., polyphosphazene, polyphosphonate, polysilanes,polysilazanes). In some embodiments, the polymer may be selected frompoly(n-pentene-2), polypropylene, polytetrafluoroethylene, polyamides(e.g., polyamide (Nylon), poly(ϵ-caprolactam) (Nylon 6),poly(hexamethylene adipamide) (Nylon 66)), polyimides (e.g.,polynitrile, and poly(pyromellitimide-1,4-diphenyl ether) (Kapton®)(NOMEX®) (KEVLAR®)), polyether ether ketone (PEEK), and combinationsthereof.

The mechanical and electronic properties (e.g., conductivity,resistivity) of these polymers are known. Accordingly, those of ordinaryskill in the art can choose suitable materials based on their mechanicaland/or electronic properties (e.g., ionic and/or electronicconductivity/resistivity), and/or can modify such polymers to beionically conducting (e.g., conductive towards single ions) based onknowledge in the art, in combination with the description herein. Forexample, the polymer materials listed above and herein may furthercomprise salts, for example, lithium salts (e.g., LiSCN, LiBr, LiI,LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity, ifdesired.

The separator may be porous. In some embodiments, the separator poresize may be, for example, less than 5 microns. In certain embodiments,the separator pore size may be between 50 nm and 5 microns, between 50nm and 500 nm, between 100 nm and 300 nm, between 300 nm and 1 micron,between 500 nm and 5 microns. In some embodiments, the pore size may beless than or equal to 5 microns, less than or equal to 1 micron, lessthan or equal to 500 nm, less than or equal to 300 nm, less than orequal to 100 nm, or less than or equal to 50 nm. In some embodiments,the pore size may be greater than 50 nm, greater than 100 nm, greaterthan 300 nm, greater than 500 nm, or greater than 1 micron. Other valuesare also possible. Combinations of the above-noted ranges are alsopossible (e.g., a pore size of less than 300 nm and greater than 100nm). In certain embodiments, the separator may be substantiallynon-porous.

As described herein, in certain embodiments, the electrochemical cellcomprises an electrolyte. The electrolytes used in electrochemical orbattery cells can function as a medium for the storage and transport ofions, and in the special case of solid electrolytes and gelelectrolytes, these materials may additionally function as a separatorbetween the anode and the cathode. Any suitable liquid, solid, or gelmaterial capable of storing and transporting ions may be used, so longas the material facilitates the transport of ions (e.g., lithium ions)between the anode and the cathode. The electrolyte is electronicallynon-conductive to prevent short circuiting between the anode and thecathode. In some embodiments, the electrolyte may comprise a non-solidelectrolyte.

In some embodiments, the additive and/or additive precursor is at leastpartially soluble in the electrolyte. In certain embodiments, theadditive and/or additive precursor is substantially soluble in theelectrolyte. In some embodiments, the additive and/or additive precursorhas a solubility in the electrolyte of at least about 1% (w/w), at leastabout 2% (w/w), at least about 5% (w/w), at least about 10% (w/w), or atleast about 15% (w/w). In certain embodiments, the additive and/oradditive precursor has a solubility in the electrolyte of less than orequal to about 20% (w/w), less than or equal to about 15% (w/w), lessthan or equal to about 10% (w/w), less than or equal to about 5% (w/w),or less than or equal to about 2% (w/w). Combinations of theabove-referenced ranges are also possible (e.g., at least about 1% (w/w)and less than or equal to about 20% (w/w)). Other ranges are alsopossible. Solubility, as used herein, is measured at 25° C. and 1 atm.In some embodiments, an electrolyte is in the form of a layer having aparticular thickness. An electrolyte layer may have a thickness of, forexample, at least 1 micron, at least 5 microns, at least 10 microns, atleast 15 microns, at least 20 microns, at least 25 microns, at least 30microns, at least 40 microns, at least 50 microns, at least 70 microns,at least 100 microns, at least 200 microns, at least 500 microns, or atleast 1 mm. In some embodiments, the thickness of the electrolyte layeris less than or equal to 1 mm, less than or equal to 500 microns, lessthan or equal to 200 microns, less than or equal to 100 microns, lessthan or equal to 70 microns, less than or equal to 50 microns, less thanor equal to 40 microns, less than or equal to 30 microns, less than orequal to 20 microns, less than or equal to 10 microns, or less than orequal to 50 microns. Other values are also possible. Combinations of theabove-noted ranges are also possible.

In some embodiments, the electrolyte includes a non-aqueous electrolyte.Suitable non-aqueous electrolytes may include organic electrolytes suchas liquid electrolytes, gel polymer electrolytes, and solid polymerelectrolytes. These electrolytes may optionally include one or moreionic electrolyte salts (e.g., to provide or enhance ionic conductivity)as described herein. Examples of useful non-aqueous liquid electrolytesolvents include, but are not limited to, non-aqueous organic solvents,such as, for example, N-methyl acetamide, acetonitrile, acetals, ketals,esters (e.g., esters of carbonic acid), carbonates (e.g., ethylenecarbonate, dimethyl carbonate), sulfones, sulfites, sulfolanes,suflonimidies (e.g., bis(trifluoromethane)sulfonimide lithium salt).aliphatic ethers, acyclic ethers, cyclic ethers, glymes, polyethers,phosphate esters (e.g., hexafluorophosphate), siloxanes, dioxolanes,N-alkylpyrrolidones, nitrate containing compounds, substituted forms ofthe foregoing, and blends thereof. Examples of acyclic ethers that maybe used include, but are not limited to, diethyl ether, dipropyl ether,dibutyl ether, dimethoxymethane, trimethoxymethane, 1,2-dimethoxyethane,diethoxyethane, 1,2-dimethoxypropane, and 1,3-dimethoxypropane. Examplesof cyclic ethers that may be used include, but are not limited to,tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, 1,4-dioxane,1,3-dioxolane, and trioxane. Examples of polyethers that may be usedinclude, but are not limited to, diethylene glycol dimethyl ether(diglyme), triethylene glycol dimethyl ether (triglyme), tetraethyleneglycol dimethyl ether (tetraglyme), higher glymes, ethylene glycoldivinyl ether, diethylene glycol divinyl ether, triethylene glycoldivinyl ether, dipropylene glycol dimethyl ether, and butylene glycolethers. Examples of sulfones that may be used include, but are notlimited to, sulfolane, 3-methyl sulfolane, and 3-sulfolene. Fluorinatedderivatives of the foregoing are also useful as liquid electrolytesolvents.

In some cases, mixtures of the solvents described herein may also beused. For example, in some embodiments, mixtures of solvents areselected from the group consisting of 1,3-dioxolane and dimethoxyethane,1,3-dioxolane and diethyleneglycol dimethyl ether, 1,3-dioxolane andtriethyleneglycol dimethyl ether, and 1,3-dioxolane and sulfolane. Theweight ratio of the two solvents in the mixtures may range, in somecases, from about 5 wt %:95 wt % to 95 wt %:5 wt %.

Non-limiting examples of suitable gel polymer electrolytes includepolyethylene oxides, polypropylene oxides, polyacrylonitriles,polysiloxanes, polyimides, polyphosphazenes, polyethers, sulfonatedpolyimides, perfluorinated membranes (NAFION resins), polydivinylpolyethylene glycols, polyethylene glycol diacrylates, polyethyleneglycol dimethacrylates, derivatives of the foregoing, copolymers of theforegoing, cross-linked and network structures of the foregoing, andblends of the foregoing.

Non-limiting examples of suitable solid polymer electrolytes includepolyethers, polyethylene oxides, polypropylene oxides, polyimides,polyphosphazenes, polyacrylonitriles, polysiloxanes, derivatives of theforegoing, copolymers of the foregoing, cross-linked and networkstructures of the foregoing, and blends of the foregoing.

In some embodiments, the non-aqueous electrolyte comprises at least onelithium salt. For example, in some cases, the at least one lithium saltis selected from the group consisting of LiNO₃, LiPF₆, LiBF₄, LiClO₄,LiAsF₆, Li₂SiF₆, LiSbF₆, LiAlCl₄, lithium bis-oxalatoborate, LiCF₃SO₃,LiN(SO₂F)₂, LiC(CnF_(2n+1)SO₂)₃, wherein n is an integer in the range offrom 1 to 20, and (C_(n)F_(2n+1)SO₂)_(m)XLi with n being an integer inthe range of from 1 to 20, m being 1 when X is selected from oxygen orsulfur, m being 2 when X is selected from nitrogen or phosphorus, and mbeing 3 when X is selected from carbon or silicon.

In some embodiments, specific combinations of additives and lithiumsalts in the electrolyte may be present in an electrochemical cell orcomponent(s) of an electrochemical cell. For example, in someembodiments an electrochemical cell or component(s) of anelectrochemical cell may comprise both lithium bis-oxalatoborate and anadditive that comprises a structure as in Formula (I):

wherein each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², NR², CR² ₂, and SiR² ₂, each R¹ and R² canbe the same or different, optionally connected, and are independentlyselected from the group consisting of hydrogen, oxygen, sulfur, halogen,nitrogen, phosphorus, substituted or unsubstituted, branched orunbranched aliphatic, substituted or unsubstituted cyclic, substitutedor unsubstituted, branched or unbranched acyclic, substituted orunsubstituted, branched or unbranched heteroaliphatic, substituted orunsubstituted, branched or unbranched acyl, substituted or unsubstitutedaryl, and substituted or unsubstituted heteroaryl, and wherein theadditive and any additive precursor is/are different from the first andsecond active electrode species. In some embodiments, the additive thatcomprises a structure as in Formula (I) and lithium bis-oxalatoboratemay be present in an electrolyte.

In some embodiments, the electrochemical cell may comprise both lithiumbis-oxalatoborate and one or more of an ethyl xanthate salt, adiethiocarbamate salt, and an isopropyl xanthate salt as describedherein. In some embodiments, such components may be present in anelectrolyte. The electrochemical cell may also include first and secondelectrodes as described herein.

In some embodiments, the combination of lithium bis-oxalatoborate withan additive comprising a structure as in Formula (I) may be present inan electrochemical cell, wherein the electrochemical cell comprises afirst electrode as describe herein (e.g., a lithium-containingelectrode) and a second electrode. The second electrode may be anintercalation electrode (e.g., a lithium intercalation electrode) suchas Li_(x)CoO₂, Li_(x)NiO₂, Li_(x)MnO₂, Li_(x)Mn₂O₄, Li_(x)FePO₄,Li_(x)CoPO₄, Li_(x)MnPO₄, and Li_(x)NiPO₄, where (0<x≤1), andLiNi_(x)Mn_(y)Co_(z)O₂ where (x+y+z=1). Formula (I) is represented by:

wherein each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², NR², CR² ₂, and SiR² ₂, each R¹ and R² canbe the same or different, optionally connected, and are independentlyselected from the group consisting of hydrogen, oxygen, sulfur, halogen,nitrogen, phosphorus, substituted or unsubstituted, branched orunbranched aliphatic, substituted or unsubstituted cyclic, substitutedor unsubstituted, branched or unbranched acyclic, substituted orunsubstituted, branched or unbranched heteroaliphatic, substituted orunsubstituted, branched or unbranched acyl, substituted or unsubstitutedaryl, and substituted or unsubstituted heteroaryl, and wherein theadditive and any additive precursor is/are different from the first andsecond active electrode species. In some embodiments, the additive thatcomprises a structure as in Formula (I) and lithium bis-oxalatoboratemay be present in an electrolyte.

In some embodiments, an electrolyte, a cathode, an additive, and/or acomponent including an additive (e.g. a layer) comprises a nitrate orother N—O compound. Examples of NO compounds include, but are notlimited to, families such as inorganic nitrates, organic nitrates,inorganic nitrites, organic nitrites, organic nitro compounds, compoundswith negatively, neutral and positively charged NO_(x) groups, and otherorganic N—O compounds. Examples of inorganic nitrates that may be usedinclude, but are not limited to, lithium nitrate, potassium nitrate,cesium nitrate, barium nitrate, and ammonium nitrate. Examples oforganic nitrates that may be used include, but are not limited to,dialkyl imidazolium nitrates, guanidine nitrate, and pyridine nitrate.Examples of inorganic nitrites that may be used include, but are notlimited to, lithium nitrite, potassium nitrite, cesium nitrite, andammonium nitrite. Examples of organic nitrites that may be used include,but are not limited to, ethyl nitrite, propyl nitrite, butyl nitrite,pentyl nitrite, and octyl nitrite. Examples organic nitro compounds thatmay be used include, but are not limited to, nitromethane, nitropropane,nitrobutanes, nitrobenzene, dinitrobenzene, nitrotoluene,dinitrotoluene, nitropyridine, and dinitropyridine. Examples of otherorganic N—O compounds that may be used include, but are not limited to,pyridine N-oxide, alkylpyridine N-oxides, and tetramethyl piperidineN-oxyl (TEMPO). These and other additives are described in more detailin U.S. Pat. No. 7,553,590, entitled “Electrolytes for lithium sulfurcells,” which is incorporated herein by reference in its entirety.Electrochemical cells comprising an additive and/or additive precursordescribed herein and a nitrate may, in some cases, increase the lifecycle of electrochemical cells as compared to electrochemical cellswithout the additive or additive precursor.

In some embodiments, the nitrate or other N—O compound is present in anelectrolyte, a cathode, an additive, and/or a component including anadditive (e.g. a layer) in an amount of at least about 0.01 wt %, atleast about 0.05 wt %, at least about 0.1 wt %, at least about 0.5 wt %,at least about 1 wt %, at least about 2 wt %, at least about 5 wt %, atleast about 10 wt %, or at least about 15 wt % versus the totalelectrolyte weight, total cathode weight, total additive weight, and/ortotal weight of the component including an additive (e.g., a layer),respectively. In certain embodiments, the nitrate or other N—O compoundis present in the electrolyte, a cathode, an additive, and/or acomponent including an additive (e.g. a layer) in an amount of less thanor equal to about 20 wt %, less than or equal to about 15 wt %, lessthan or equal to about 10 wt %, less than or equal to about 5 wt %, lessthan or equal to about 2 wt %, less than or equal to about 1 wt %, lessthan or equal to about 0.5 wt %, less than or equal to about 0.1 wt %,or less than or equal to about 0.05 wt % versus the total electrolyteweight, total cathode weight, total additive weight, and/or total weightof the component including an additive (e.g., a layer), respectively.Combinations of the above-referenced ranges are also possible (e.g., atleast about 0.01 wt % and less than or equal to about 20 wt %). Otherranges are also possible.

In some embodiments, an electrochemical cell described herein comprisesat least one current collector. Materials for the current collector maybe selected, in some cases, from metals (e.g., copper, nickel, aluminum,passivated metals, and other appropriate metals), metallized polymers,electrically conductive polymers, polymers comprising conductiveparticles dispersed therein, and other appropriate materials. In certainembodiments, the current collector is deposited onto the electrode layerusing physical vapor deposition, chemical vapor deposition,electrochemical deposition, sputtering, doctor blading, flashevaporation, or any other appropriate deposition technique for theselected material. In some cases, the current collector may be formedseparately and bonded to the electrode structure. It should beappreciated, however, that in some embodiments a current collectorseparate from the electroactive layer may not be needed.

For convenience, certain terms employed in the specification, examples,and appended claims are listed here. Definitions of specific functionalgroups and chemical terms are described in more detail below. Forpurposes of this invention, the chemical elements are identified inaccordance with the Periodic Table of the Elements, CAS version,Handbook of Chemistry and Physics, 75th Ed., inside cover, and specificfunctional groups are generally defined as described therein.Additionally, general principles of organic chemistry, as well asspecific functional moieties and reactivity, are described in OrganicChemistry, Thomas Sorrell, University Science Books, Sausalito: 1999.

The term “aliphatic,” as used herein, includes both saturated andunsaturated, nonaromatic, straight chain (i.e., unbranched), branched,acyclic, and cyclic (i.e., carbocyclic) hydrocarbons, which areoptionally substituted with one or more functional groups. As will beappreciated by one of ordinary skill in the art, “aliphatic” is intendedherein to include, but is not limited to, alkyl, alkenyl, alkynyl,cycloalkyl, cycloalkenyl, and cycloalkynyl moieties. Thus, as usedherein, the term “alkyl” includes straight, branched and cyclic alkylgroups. An analogous convention applies to other generic terms such as“alkenyl”, “alkynyl”, and the like. Furthermore, as used herein, theterms “alkyl”, “alkenyl”, “alkynyl”, and the like encompass bothsubstituted and unsubstituted groups. In certain embodiments, as usedherein, “aliphatic” is used to indicate those aliphatic groups (cyclic,acyclic, substituted, unsubstituted, branched or unbranched) having 1-20carbon atoms. Aliphatic group substituents include, but are not limitedto, any of the substituents described herein, that result in theformation of a stable moiety (e.g., aliphatic, alkyl, alkenyl, alkynyl,heteroaliphatic, heterocyclic, aryl, heteroaryl, acyl, oxo, imino,thiooxo, cyano, isocyano, amino, azido, nitro, hydroxyl, thiol, halo,aliphaticamino, heteroaliphaticamino, alkylamino, heteroalkylamino,arylamino, heteroarylamino, alkylaryl, arylalkyl, aliphaticoxy,heteroaliphaticoxy, alkyloxy, heteroalkyloxy, aryloxy, heteroaryloxy,aliphaticthioxy, heteroaliphaticthioxy, alkylthioxy, heteroalkylthioxy,arylthioxy, heteroarylthioxy, acyloxy, and the like, each of which mayor may not be further substituted).

The term “alkyl” refers to the radical of saturated aliphatic groups,including straight-chain alkyl groups, branched-chain alkyl groups,cycloalkyl (alicyclic) groups, alkyl substituted cycloalkyl groups, andcycloalkyl substituted alkyl groups. The alkyl groups may be optionallysubstituted, as described more fully below. Examples of alkyl groupsinclude, but are not limited to, methyl, ethyl, propyl, isopropyl,butyl, isobutyl, tert-butyl, 2-ethylhexyl, cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, and the like. “Heteroalkyl” groups are alkylgroups wherein at least one atom is a heteroatom (e.g., oxygen, sulfur,nitrogen, phosphorus, etc.), with the remainder of the atoms beingcarbon atoms. Examples of heteroalkyl groups include, but are notlimited to, alkoxy, poly(ethylene glycol)-, alkyl-substituted amino,tetrahydrofuranyl, piperidinyl, morpholinyl, etc.

The terms “alkenyl” and “alkynyl” refer to unsaturated aliphatic groupsanalogous to the alkyl groups described above, but containing at leastone double or triple bond respectively. The “heteroalkenyl” and“heteroalkynyl” refer to alkenyl and alkynyl groups as described hereinin which one or more atoms is a heteroatom (e.g., oxygen, nitrogen,sulfur, and the like).

The term “aryl” refers to an aromatic carbocyclic group having a singlering (e.g., phenyl), multiple rings (e.g., biphenyl), or multiple fusedrings in which at least one is aromatic (e.g.,1,2,3,4-tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl), alloptionally substituted. “Heteroaryl” groups are aryl groups wherein atleast one ring atom in the aromatic ring is a heteroatom, with theremainder of the ring atoms being carbon atoms. Examples of heteroarylgroups include furanyl, thienyl, pyridyl, pyrrolyl, N lower alkylpyrrolyl, pyridyl N oxide, pyrimidyl, pyrazinyl, imidazolyl, indolyl andthe like, all optionally substituted.

The terms “amine” and “amino” refer to both unsubstituted andsubstituted amines, e.g., a moiety that can be represented by thegeneral formula: N(R′)(R″)(R′″) wherein R′, R″, and R′″ eachindependently represent a group permitted by the rules of valence.

The terms “acyl,” “carboxyl group,” or “carbonyl group” are recognizedin the art and can include such moieties as can be represented by thegeneral formula:

wherein W is H, OH, O-alkyl, O-alkenyl, or a salt thereof. Where W isO-alkyl, the formula represents an “ester.” Where W is OH, the formularepresents a “carboxylic acid.” In general, where the oxygen atom of theabove formula is replaced by sulfur, the formula represents a“thiolcarbonyl” group. Where W is a S-alkyl, the formula represents a“thiolester.” Where W is SH, the formula represents a “thiolcarboxylicacid.” On the other hand, where W is alkyl, the above formula representsa “ketone” group. Where W is hydrogen, the above formula represents an“aldehyde” group.

As used herein, the term “heteroaromatic” or “heteroaryl” means amonocyclic or polycyclic heteroaromatic ring (or radical thereof)comprising carbon atom ring members and one or more heteroatom ringmembers (such as, for example, oxygen, sulfur or nitrogen). Typically,the heteroaromatic ring has from 5 to about 14 ring members in which atleast 1 ring member is a heteroatom selected from oxygen, sulfur, andnitrogen. In another embodiment, the heteroaromatic ring is a 5 or 6membered ring and may contain from 1 to about 4 heteroatoms. In anotherembodiment, the heteroaromatic ring system has a 7 to 14 ring membersand may contain from 1 to about 7 heteroatoms. Representativeheteroaryls include pyridyl, furyl, thienyl, pyrrolyl, oxazolyl,imidazolyl, indolizinyl, thiazolyl, isoxazolyl, pyrazolyl, isothiazolyl,pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, triazolyl, pyridinyl,thiadiazolyl, pyrazinyl, quinolyl, isoquinolyl, indazolyl, benzoxazolyl,benzofuryl, benzothiazolyl, indolizinyl, imidazopyridinyl, isothiazolyl,tetrazolyl, benzimidazolyl, benzoxazolyl, benzothiazolyl,benzothiadiazolyl, benzoxadiazolyl, carbazolyl, indolyl,tetrahydroindolyl, azaindolyl, imidazopyridyl, qunizaolinyl, purinyl,pyrrolo[2,3]pyrimidyl, pyrazolo[3,4]pyrimidyl, benzo(b)thienyl, and thelike. These heteroaryl groups may be optionally substituted with one ormore substituents.

The term “substituted” is contemplated to include all permissiblesubstituents of organic compounds, “permissible” being in the context ofthe chemical rules of valence known to those of ordinary skill in theart. In some cases, “substituted” may generally refer to replacement ofa hydrogen with a substituent as described herein. However,“substituted,” as used herein, does not encompass replacement and/oralteration of a key functional group by which a molecule is identified,e.g., such that the “substituted” functional group becomes, throughsubstitution, a different functional group. For example, a “substitutedphenyl” must still comprise the phenyl moiety and cannot be modified bysubstitution, in this definition, to become, e.g., a heteroaryl groupsuch as pyridine. In a broad aspect, the permissible substituentsinclude acyclic and cyclic, branched and unbranched, carbocyclic andheterocyclic, aromatic and nonaromatic substituents of organiccompounds. Illustrative substituents include, for example, thosedescribed herein. The permissible substituents can be one or more andthe same or different for appropriate organic compounds. For purposes ofthis invention, the heteroatoms such as nitrogen may have hydrogensubstituents and/or any permissible substituents of organic compoundsdescribed herein which satisfy the valencies of the heteroatoms. Thisinvention is not intended to be limited in any manner by the permissiblesubstituents of organic compounds.

Examples of substituents include, but are not limited to, alkyl, aryl,aralkyl, cyclic alkyl, heterocycloalkyl, hydroxy, alkoxy, aryloxy,perhaloalkoxy, aralkoxy, heteroaryl, heteroaryloxy, heteroarylalkyl,heteroaralkoxy, azido, amino, halogen, alkylthio, oxo, acyl, acylalkyl,carboxy esters, carboxyl, carboxamido, nitro, acyloxy, aminoalkyl,alkylaminoaryl, alkylaryl, alkylaminoalkyl, alkoxyaryl, arylamino,aralkylamino, alkylsulfonyl, carboxamidoalkylaryl, carboxamidoaryl,hydroxyalkyl, haloalkyl, alkylaminoalkylcarboxy, aminocarboxamidoalkyl,alkoxyalkyl, perhaloalkyl, arylalkyloxyalkyl, and the like.

The following examples are intended to illustrate certain embodiments ofthe present invention, but do not exemplify the full scope of theinvention.

EXAMPLES

In the examples below, an additive was introduced into the electrolyteand resulted in cycle life increases for electrochemical cells having alithium metal anode/lithium iron phosphate cathode (Examples 1-2) and inLi—S cells in a Beta-2 design (Example 3), and for electrochemical cellshaving a lithium metal anode/nickel cobalt manganese cathode (Example4). The weight percentage of the additive was based on the weight of theelectrolyte and is listed below. Additive was introduced into two typesof electrolytes:

1. EC/DMC LiPF₆ (Examples 1-2)

2. DME/DOL+LiTFSI+LiNO₃ (Example 3)

The cells were cycled at a normal rate (C/5 discharge and C/8 charge)and at accelerated test conditions: 1C rate discharge and C/3 ratecharge.

Example 1

Electrochemical cells were assembled with a lithium iron phosphatecathode received from Enertech (Korea). A vacuum deposited Li anode withthickness of 8.8 um and a Celgard 2325 separator were used. The cathodetotal active area was 99.441 cm². Cells were filled with 0.5 ml of threeelectrolytes:

-   -   Electrolyte 1-1: Ethylene Carbonate, 44.1 wt %; Dimethyl        Carbonate, 44.1 wt %; LiPF₆, 11.8 wt %. (Comparative        Electrolyte)    -   Electrolyte 1-2: 98.5 wt % of Electrolyte 1-1 and 1.5 wt % of        Potassium Ethyl Xanthate (additive)    -   Electrolyte 1-3: 98 wt % of Electrolyte 1-1 and 2 wt % of        Lithium Diethyl Dithiocarbamate (additive)

The weight percentage of the additives were based on the total weight ofthe electrolyte and additive.

Each cell was sealed in the pouch made of Showa Denko packagingmaterial. Cell electrical testing was performed while applying 10 kg/cm²of anisotropic pressure perpendicular to the electrodes surface. Cellsat first cycle were charged at a current of 17 mA to a voltage of 4.2 Vand discharged at a current 27 mA to a voltage of 2.5 V. All cellsdelivered a first cycle discharge capacity of 135-137 mAh. At subsequentcycles the charge current was increased to 45 mA and the dischargecurrent was increased to 137 mA. The cell cycle life was evaluated tothe point when discharge capacity dropped below 100 mAh and is shown inFIG. 2. Specifically, cycle life delivered by three electrolytes islisted below:

Electrolyte 1-1: 46 cycles (Comparative Electrolyte)Electrolyte 1-2: 323 cyclesElectrolyte 1-3: 272 cycles

This example shows that the addition of an additive comprising axanthate or dithiocarbamate to the electrolyte of an electrochemicalcell can significantly increase the cycle life of the electrochemicalcell.

Example 2

Cells were assembled with Nickel Cobalt Manganese (NCM) cathode receivedfrom Enertech (Korea). Vacuum deposited Li anode with thickness of 11 umand a Celgard 2325 separator were used. The cathode total active areawas 99.441 cm². The cells were filled with 0.55 ml of four electrolytes:

-   -   Electrolyte 2-1: Ethylene Carbonate 44.1 wt %, Dimethyl        Carbonate 44.1 wt %, LiPF6 11.8 w %. (Comparative Electrolyte)    -   Electrolyte 2-2: 98 wt % of Electrolyte 2-1 and 2 wt % of        Potassium Ethyl Xanthate (additive)    -   Electrolyte 2-3: 98 wt % of Electrolyte 2-1 and 2 wt % of        Potassium Isopropyl Xanthate (additive)    -   Electrolyte 2-4: 98 wt % of Electrolyte 2-1 and 2 wt % of        Lithium Diethyl Dithiocarbamate (additive)

The weight percentage of the additive was based on the total weight ofthe electrolyte and additive.

Each cell was sealed in the pouch made of Showa Denko packagingmaterial. Cells electrical testing was performed while applying 10kg/cm² of anisotropic pressure perpendicular to the surface of theelectrodes. Cells at the first cycle were charged at a current of 20 mAto a voltage of 4.35 V and discharged at a current of 34 mA to a voltageof 3.2 V. All cells delivered first cycle discharge capacity of 187-190mAh. At subsequent cycles, the charge current was increased to 57 mA andthe discharge current was increased to 170 mA. The cell cycle life wasevaluated to the point when discharge capacity dropped below 150 mAh.

Cycle life delivered by four electrolytes is listed below and shown inFIG. 3:

Electrolyte 2-1: 33 cycles (Comparative Electrolyte)Electrolyte 2-2: 41 cycleElectrolyte 2-3: 104 cyclesElectrolyte 2-4: 110 cycles

This example shows that the addition of an additive comprising axanthate or dithiocarbamate to the electrolyte of an electrochemicalcell can increase the cycle life of the electrochemical cell.

Example 3

Beta-2 cells, as described here, were assembled with a sulfur cathodecoated at Sion Power. The cathode formulation included S-75 wt %, Carbonblack-24 wt %, PVOH binder 1 wt %. The sulfur coated loading was of 1.87mg/cm². The cells included a Li foil anode with a thickness of 50 um andTonen separator with thickness of 9 um. Cathode total active area was1289 cm². Different cells were filled with 7 g of one of threeelectrolytes:

Electrolyte 3-1: 1,3-Dioxolane 43.3 wt %, 1,2-Dimethoxyethane 43.3 wt %,LiTFSI 8 w %, LiNO₃ 4 wt %, Guanidine Nitrate 1 wt %, Pyridine Nitrate0.4 wt %. (Comparative Electrolyte)

Electrolyte 3-2: 98 wt % of Electrolyte 3-1 and 2 wt % of PotassiumEthyl Xanthate.

Electrolyte 3-3: 98 wt % of Electrolyte 3-1 and 2 wt % of PotassiumIsopropyl Xanthate.

Each cell was sealed in the pouch made of Showa Denko packagingmaterial. Cells were discharged at current 0.5 A to voltage 1.7 V andcharged at current 0.315 A to voltage of 2.5 V. All cells deliveredfifth cycle discharge capacity of 2.85-2.87 Ah. Cells cycle life wasevaluated to the point when discharge capacity dropped below 1.75 Ah.

Cycle life delivered by three electrolytes is listed below and shown inFIG. 4:

Electrolyte 3-1: 33 cycles (Comparative Electrolyte)Electrolyte 3-2: 40 cyclesElectrolyte 3-3: 46 cycles

This example shows the life cycle improvement of electrochemical cellsincluding additives described herein for lithium cells having a sulfurcathode.

Example 4

This example illustrates the life cycle improvement of additivescombined with LiNO₃.

Cells were assembled with Nickel Cobalt Manganese (NCM) cathode receivedfrom Enertech (Korea). Vacuum deposited Li anode with thickness of 8 umand a Celgard 2325 separator were used. The cathode total active areawas 99.441 cm². Four kinds of cells were assembled:

-   -   Cell 1: NCM cathode, 8 um Li anode and 0.55 ml of Electrolyte        4-1 (Ethylene Carbonate 44.1 wt %, Dimethyl Carbonate 44.1 wt %,        LiPF₆ 11.8 wt %).    -   Cell 2: NCM cathode, 8 um Li anode and 0.55 ml of Electrolyte        4-2 (98 wt % of Electrolyte 4-1 and 2 wt % of Potassium Ethyl        Xanthate).    -   Cell 3: NCM cathode treated with solution of LiNO₃ in methanol        and then dried at 130° C. Amount of LiNO₃ in the dry cathode was        0.1 mg/cm². Cathode was combined with 8 micron thickness Li        anode and 0.55 ml of Electrolyte 4-1.    -   Cell 4: Cathode with LiNO₃ from 3 was combined with 8 um Li        anode and 0.55 ml of Electrolyte 4-2 (98 wt % of Electrolyte 4-1        and 2 wt % of Potassium Ethyl Xanthate).

Each cell was sealed in the pouch made of Showa Denko packagingmaterial. Cells electrical testing was performed while applying 10kg/cm² of anisotropic pressure perpendicular to the surface of theelectrodes. Cells at the first 25 cycles were charged at a current of 20mA to a voltage of 4.20 V and discharged at a current of 34 mA to avoltage of 3.2 V. After 25 cycles charge voltage was increased to 4.35V. All cells delivered discharge capacity of 183-188 mAh. The cell cyclelife was evaluated to the point when discharge capacity dropped below140 mAh. Cycle life for each cell is listed below and shown in FIG. 5:

Cell 1: 52 cycles

Cell 2: 77 cycles

Cell 3: 91 cycle

Cell 4: 250 cycles

This example shows the life cycle improvement of electrochemical cellsincluding additives described herein for lithium cells having a nickelcobalt manganese cathode.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

What is claimed is:
 1. An electrochemical cell, comprising: a firstelectrode; an electrolyte comprising a fluorinated carbonate; anadditive having a structure as in Formula (I) and/or an additiveprecursor having a structure as in Formula (II):

wherein: each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², CR² ₂, and SiR² ₂; n is 1-6; and each R¹and R² are the same or different, optionally connected, and areindependently selected from the group consisting of hydrogen; oxygen;sulfur; halogen; nitrogen; phosphorus; substituted or unsubstituted,branched or unbranched aliphatic; substituted or unsubstituted cyclic;substituted or unsubstituted, branched or unbranched acyclic;substituted or unsubstituted, branched or unbranched heteroaliphatic;substituted or unsubstituted, branched or unbranched acyl; substitutedor unsubstituted aryl; and substituted or unsubstituted heteroaryl. 2.An electrochemical cell, comprising: a first electrode; an electrolytecomprising a fluorinated carbonate; an additive having a structure as inFormula (I) and/or an additive precursor having a structure as inFormula (II):

wherein: each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², NR², CR² ₂, and SiR² ₂; n is 1-6; each R¹and R² are the same or different, optionally connected, and areindependently selected from the group consisting of hydrogen; oxygen;sulfur; halogen; nitrogen; phosphorus; substituted or unsubstituted,branched or unbranched aliphatic; substituted or unsubstituted cyclic;substituted or unsubstituted, branched or unbranched acyclic;substituted or unsubstituted, branched or unbranched heteroaliphatic;substituted or unsubstituted, branched or unbranched acyl; substitutedor unsubstituted aryl; and substituted or unsubstituted heteroaryl. 3.An electrochemical cell, comprising: a first electrode comprising afirst active electrode species; an electrolyte comprising a fluorinatedcarbonate; an additive having a structure as in Formula (I) and/or anadditive precursor having a structure as in Formula (II):

wherein: each occurrence of Q is independently selected from the groupconsisting of Se, O, S, PR², NR², CR² ₂, and SiR² ₂; n is 1-6; each R¹and R² are the same or different, optionally connected, and areindependently selected from the group consisting of hydrogen; oxygen;sulfur; halogen; nitrogen; phosphorus; substituted or unsubstituted,branched or unbranched aliphatic; substituted or unsubstituted cyclic;substituted or unsubstituted, branched or unbranched acyclic;substituted or unsubstituted, branched or unbranched heteroaliphatic;substituted or unsubstituted, branched or unbranched acyl; substitutedor unsubstituted aryl; and substituted or unsubstituted heteroaryl; andwherein the additive and/or the additive precursor is/are different fromthe first electrode species.
 4. The electrochemical cell of claim 2,wherein the fluorinated carbonate comprises fluorinated ethylenecarbonate.
 5. The electrochemical cell of claim 2, further comprising alithium salt.
 6. The electrochemical cell of claim 2, wherein theadditive and/or additive precursor is polyanionic.
 7. Theelectrochemical cell of claim 2, wherein the additive is a salt.
 8. Theelectrochemical cell of claim 2, wherein the additive comprises acation.
 9. The electrochemical cell of claim 8, wherein the cation isselected from the group consisting of Li⁺, Na⁺, K⁺, Cs⁺, Rb⁺, Ca⁺²,Mg⁺², substituted or unsubstituted ammonium, guanidinium andimidazolium.
 10. The electrochemical cell of claim 2, wherein theadditive and/or additive precursor comprises a xanthate group.
 11. Theelectrochemical cell of claim 2, wherein at least a portion of theadditive and/or additive precursor is in solid form.
 12. Theelectrochemical cell of claim 2, wherein at least a portion of theadditive and/or additive precursor is dissolved in the electrolyte. 13.The electrochemical cell of claim 2, wherein the additive and/oradditive precursor is disposed on and/or within the first electrode. 14.The electrochemical cell of claim 2, wherein the electrochemical cellcomprises a second electrode, and the additive and/or additive precursoris disposed on and/or within the second electrode.
 15. Theelectrochemical cell of claim 2, wherein the electrochemical cellcomprises a second electrode, and wherein the second electrode is anintercalated electrode.
 16. the electrochemical cell of claim 2, whereinthe additive and any additive precursor is present in the electrolyte ina total amount ranging between about 0.5 wt % and about 20 wt % versusthe total weight of the electrolyte and additive and/or additiveprecursor.
 17. The electrochemical cell of claim 2, the electrochemicalcell comprises a second electrode, and wherein the additive and anyadditive precursor is present in the electrolyte in a total amountranging between about 0.5 wt % and about 4 wt % versus the weight ofeach of the first and second electrodes.
 18. The electrochemical cell ofclaim 2, the electrochemical cell comprises a second electrode, andwherein the additive and/or additive precursor is disposed on and/orwithin a separator positioned between the first electrode and the secondelectrode.
 19. The electrochemical cell of claim 2, wherein theelectrolyte comprises a nitrate.
 20. The electrochemical cell of claim2, further comprising a lithium bis-oxalatoborate species.